2019 Volume 91 Issue 1 Pages 28-36
The evaluation parameter of skin formation-type solidification tendency based on the numerical simulation of plate castings for alloys and pure metals was developed, and its applicability and influential factors were investigated. The skin formation index S/T (S : skin formation range, T : plate thickness, 0≤S/T<1) was defined based on the solidification time distribution of the castings, where S/T ≳ 0.8 for steel or pure metal and/or metal mold, and S/T ＝ 0 for aluminum or copper alloy and sand mold. The higher the mold temperature and/or superheat, or the greater the interfacial heat resistance between the casting and mold, the smaller was S/T. These S/T values were also consistent with conventional dimensionless numbers capable of partly evaluating the skin formation-type solidification tendency, thus confirming the applicability of S/T as the unified evaluation parameter. For alloys under ΔT*>0.01 (ΔT* : dimensionless solidification temperature range), the casting surface temperature was the dominant factor influencing S/T. On the other hand, for alloys under ΔT* <0.01 or pure metals, ΔT* significantly affected S/T despite the surface temperature, where S/T ≳ 0.7. Use of S/T enables the evaluation of behavior not reflected in the dimensionless numbers. In addition, the combined use of S/T with end or riser effects allows the evaluation of solidification characteristics.
